1. Field of the Invention
The present invention relates to a bracket angle adjustment mechanism.
2. Description of the Related Art
Heretofore, there has been known one type of bracket angle adjustment mechanism. For example, in a vehicle seat assembly 1 as shown in FIG. 21, the bracket angle adjustment mechanism comprises a first bracket 4 fixed to a seat cushion 2, and a second bracket 5 fixed to a seat back 3, wherein a handle 7 fixed to a control shaft 6 is manually rotated clockwise or counterclockwise to adjust an angle of the second bracket 5 relative to the first bracket 4, i.e. a frontward/rearward reclining angle of the seat back 3 (see, for example, Japanese Patent Publication No. 63-47443: Patent Publication 1).
More specifically, the first bracket 4 includes an external-tooth gear 4a, and the second bracket 5 includes an internal-tooth gear 5a which has a larger number of teeth than that of the external-tooth gear 4a. The control shaft 6 has an inward end supported by a central hole 5b of the second bracket 5.
The bracket angle adjustment mechanism further includes a pair of wedge members 11A, 11B and a spring member 12. The pair of wedge members 11A, 11B are fitted in an eccentric space 10 which is defined between an inner peripheral surface of a large-diameter hole 4a formed in a central region of the external-tooth gear 4a and an outer peripheral surface of a small-diameter shank 9a integral with or constituting a central portion of the internal-tooth gear 5a (in this conventional example, the small-diameter shank 9a corresponds to a given circumferential portion 9a of a follower disk 9 fixed to the control shaft 6), when respective portions of the external-tooth gear 4a and the internal-tooth gear 5a are engaged with one another. The spring member 12 is interposed between the pair of wedge members 11A, 11B in the eccentric space to apply a biasing force to each of the wedge members 11A, 11B in a wedging direction, i.e. in a direction allowing each of the wedge members 11A, 11B to be wedged between the inner peripheral surface of the large-diameter central hole 4a and the outer peripheral surface of the small-diameter central shank 9a. The control shaft 6 is adapted to move a wedged-state releasing portion (which corresponds to a follower protrusion 9b formed in the follower disk 9) located between respective wedging ends of the wedge members 11A, 11B. In FIG. 21C, the reference numeral 13 indicates a cover plate fixed to the second bracket 5. The cover plate 13 extends to cover the external-tooth gear 4a of the first bracket 4, and has a bearing portion 13a supporting an outward portion of the control shaft 13a. 
In an operation for adjusting an angle of the second bracket 5 relative to the first bracket 4, i.e. a frontward/rearward reclining angle of the seat back 3, the handle 7 is manually rotated to rotate the control shaft 6. In conjunction with the rotation of the control shaft 6, the wedged-state releasing portion 9b is rotated to move the pair of wedge members 11A, 11B together with the spring member 12 circularly in the eccentric space 10, so that the small-diameter shank 9a is eccentrically moved relative to the large-diameter hole 4b to allow an engagement position of the internal-tooth gear 5a relative to the external-tooth gear 4a to be changed.
As shown in FIG. 22, there has also been known a bracket angle adjustment mechanism which comprises a pair of wedge members fitted into an eccentric space 10 defined between a large-diameter hole 4a formed in a central region of a first bracket 4 and a small-diameter shank 5c constituting a central portion of a second bracket 5, a wedged-state release member 8 having a wedged-state release portion 8a and a tubular portion 8b fitted in a small-diameter shank 5c of a second bracket 5, and a control shaft 6 fitted into and splined to the tubular portion 8b (see Japanese Patent Publication No. 07-284422: Patent Publication 2).
In the bracket angle adjustment mechanisms as disclosed in the Patent Publications 1 and 2, there remain much needs to be improved. For example, in the bracket angle adjustment mechanisms as disclosed in the Patent Publication 2, the tubular portion 8b of the wedged-state release member 8 is fitted in the small-diameter shank 5c of the second bracket 5, and the control shaft 6 is fitted into and splined to the tubular portion 8b. Thus, in connection with layout conditions, this mechanism has difficulties in increasing a thickness of the small-diameter shank 5c of the second bracket 5 and the tubular portion 8b of the wedged-state release member 8, and in including a diameter of the control shaft 6.
Moreover, this mechanism has a problem about increase in production cost due to the need for the spline connection between the control shaft 6 and the tubular portion 8b of the wedged-state release member 8, and a complicated shape of the wedged-state release mechanical 8.